1. Field of the Invention
The present invention relates to a wafer plating apparatus for plating wafers for use in semiconductors.
2. Description of the Related Art
Hitherto, as a wafer plating apparatus for use in semiconductors, there is known one which performs plating while the wafer surface to be plated is laid face down, being kept in contact with the surface of a plating solution overflowing from a plating tank.
Specifically, as shown in FIG. 9, the above-described wafer plating apparatus includes a wafer clamp 6 for holding a wafer 4 with the surface to be plated 5 of the wafer 4 facing down, a wafer support member 7 capable of supporting the surface to be plated 5 over the entire peripheral edge thereof, and a plating tank 2 capable of circulating a plating solution while making the plating solution overflow from the upper opening thereof. This wafer plating apparatus is arranged so as to perform plating while the surface to be plated 5 is laid face down, being maintained in contact with the surface of the plating solution, in a state in which the wafer 4 is clamped by the wafer clamp 6 and the wafer support member 7.
After the plating has been performed, this wafer plating apparatus withdraws the wafer 4 from the plating solution and rotates the wafer 4 so as to remove the plating solution adhering to the plated surface 5. Therefore, even when a plated film prone to dissolution into the plating solution is formed, there is no risk that the plated film is dissolved by the adhering plating solution while the wafers 4 are exchanged. This results in the plated surface being provided with a superior appearance and the cleaning process in a post-treatment being simplified. Furthermore, this wafer plating apparatus has an advantage in that a uniform plated film can be formed over the entire surface to be plated 5 by rotating the wafer 4 during a plating process.
However, since the wafer support member 7 of this wafer plating apparatus typically has a wafer support portion 10 having an L-shaped cross-section, the wafer support portion 10 and the surface to be plated 5 form a corner portion C. In the the corner portion C, air contained in the plating solution remains. This is because the plating solution moves toward the peripheral edge of the surface to be plated 5, and hence the flow of the plating solution is prone to stagnate in the corner C which constitutes a small step, with the result that air contained in the plating solution also remains therein. Air, which is thus prone to remain at the peripheral edge, causes non-uniform plating at the corner portion and reduces the plating area, that is, the available area of a wafer. This is undesirable in view of the production yield.
The conventional wafer plating apparatus is arranged so that plating is not started until the air remaining on the surface to be plated is discharged to the outside to some extent, in order to suppress the above-described influence of air. As a result, if plating is conducted on a wafer surface to be plated which has been coated with a metallic film such as Cu, that is, a surface coated with a so-called seed metal, using a plating solution so as to dissolve the seed metal, the seed metal in contact with the plating solution will be dissolved while air is discharged, and consequently, uniform plating may not be performed.
It is, therefore, an object of the present invention to provide a technique for removing air remaining on the peripheral edge of the surface to be plated in the conventional wafer plating apparatus, and to provide a wafer plating apparatus capable of performing a more uniform plating up to the peripheral edge of the surface to be plated, and further capable of plating while minimizing the dissolution of the seed metal, even when the wafer is one coated with a seed metal.
In order to solve the above-described problems, the present inventors provide a wafer plating apparatus as follows. First, in a first aspect of the invention, there is provided a wafer plating apparatus which comprises a wafer support member having a wafer clamp for holding a wafer with the wafer surface to be plated facing down, and having a wafer support portion which has an L-shaped cross-section and which is capable of supporting the surface to be plated over the entire peripheral edge thereof; and a plating tank which circulates a plating solution while making the plating solution overflow from an upper opening of the tank. This wafer plating apparatus is arranged so as to perform plating, while the wafer surface to be plated is laid face down, being maintained in contact with the surface of the plating solution, in a state in which the wafer is clamped by the wafer clamp and the wafer support member. In this wafer plating apparatus, the wafer support member has air-vent grooves for discharging the air remaining on the peripheral edge of the surface to be plated while the surface of the plating solution and the wafer are in contact with each other, the air-vent grooves being formed at the lower end of the wafer support portion.
The xe2x80x9cair-vent groovesxe2x80x9d in the first aspect of the invention refers to ones which are constructed by forming a wafer support portion into a so-called comb-tooth configuration along the peripheral edge of the surface to be plated. The wafer support portion has a slight level difference to the surface to be plated. The air-vent grooves in the first invention are constructed by forming spots where this level difference has been minimized, at the lower end of the wafer support portion. Hence, the air tending to remain on the peripheral edge is discharged to the outside of the wafer support portion through these air-vent grooves, which prevents the air from remaining on the peripheral edge of the surface to be plated. In this case, the shape and the number of the air-vent grooves are not particularly limited. The optimum shape of the air-vent grooves may be appropriately determined in consideration of the scale of the wafer shape, the difference in the amount of generated air due to different plating solutions, etc.
Next, in a second aspect of the invention, the present inventors provide a wafer plating apparatus which comprises a wafer support member having a wafer clamp for holding a wafer with the wafer surface to be plated face down, and having a wafer support portion which has an L-shaped cross-section and which is capable of supporting the surface to be plated over the entire peripheral edge thereof; and a plating tank which circulates a plating solution while making the plating solution overflow from an upper opening. This wafer plating apparatus is arranged so as to perform plating, while the wafer surface to be plated is laid face down, being maintained in contact with the surface of the plating solution, and while the wafer is rotated, in a state in which the wafer is clamped by the wafer clamp and the wafer support member. In this wafer plating apparatus, the wafer support member has a spiral groove for discharging the air remaining on the peripheral edge of the surface to be plated while the surface of the plating solution and the wafer are in contact with each other, the spiral groove being formed on the inner peripheral surface side of the wafer support portion.
The xe2x80x9cinner peripheral surfacexe2x80x9d of the support portion in the second invention refers to the side which constitutes a level difference to the surface to be plated. On this inner peripheral surface, a spiral groove, a so-called thread groove, is formed. The spiral groove is formed from the side of the surface to be plated to the lower end of the wafer support portion, in the inner peripheral surface of the wafer support portion. More specifically, the spiral groove is formed so that, while the wafer is rotated, that is, while the wafer support portion is rotated, the spiral groove proceeds, with the rotation, from the side of the surface to be plated to the lower end of the wafer support portion. When the wafer plating is performed with a spiral groove provided, while the wafer is rotated, the air tending to remain on the peripheral edge enters into the spiral groove, moves along the travel direction of the spiral groove, and is ultimately discharged to the outside. In this case, the shape and the pitch of the spiral groove are not particularly limited. The optimum shape of the spiral groove may be appropriately determined in consideration of the scale of the wafer shape, the difference in the amount of generated air due to different plating solutions, etc.
Next, as a third invention, the present inventors provide a wafer plating apparatus which comprises a wafer support member having a wafer clamp for holding a wafer with the wafer surface to be plated facing down, and having a wafer support portion which has an L-shaped cross-section and which is capable of supporting the surface to be plated over the entire peripheral edge thereof; and a plating tank which circulates a plating solution while making the plating solution overflow from an upper opening. This wafer plating apparatus is arranged so as to perform plating, while the wafer surface to be plated is laid face down, being maintained in contact with the surface of the plating solution, and while the wafer is rotated, in a state in which the wafer is clamped by the wafer clamp and the wafer support member. In this wafer plating apparatus, the wafer support member has guide wings for discharging the air remaining on the peripheral edge of the surface to be plated while the surface of the plating solution and the wafer are in contact with each other, the guide wings being formed at the lower end of the wafer support portion.
The xe2x80x9cguide wingsxe2x80x9d in the third aspect of the invention refers to ones which are provided from the vicinity of the surface to be plated along the lower end of the wafer supporting portion, on the inner peripheral surface, and which are plurally arranged on the entire periphery of the wafer support portion, radially with respect to the center of the wafer. With such guide wings provided, the air tending to remain on the peripheral edge is discharged to the outside of the wafer support portion, while the wafer is rotated, that is, while the wafer support portion is rotated. In this case also, the shape and the number of the guide wings are not particularly limited. The optimum shape of the guide wings may be appropriately determined in consideration of the scale of the wafer shape, the difference in the amount of generated air due to different plating solutions, etc.
Furthermore, in the above-described first through third aspects of the invention, in order to completely remove air, and to eliminate the flow stagnation of the plating solution occurring on the peripheral edge of the surface to be plated, it is preferable that a solution-supply nozzle be provided in the plating tank, the solution-supply nozzle forcibly supplying the plating solution to the peripheral edge of the surface to be plated. This allows the plating on the peripheral edge of the surface to be more uniform.